World's biggest blue diamond may fetch $19M

By Scott Reyburn, Bloomberg News

August 29, 2013

LONDON — The world's biggest round “fancy vivid” blue diamond is expected to sell for more than $19 million at an auction in Hong Kong in October.

The brilliant-cut internally flawless stone, weighing 7.59 carats, will be auctioned by Sotheby's on Oct. 7 as part of the company's 40th anniversary sales in Asia, according to an emailed release from the New York-based auction house.

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Colored stones, which account for about 0.01 percent of mined diamonds, dominate the top end of the jewelry market. Their scarcity and aesthetic appeal have triggered record auction prices in recent years, led by the $45.6 million paid by the London-based jeweler Graff for a 24.78-carat “Fancy Intense Pink” at Sotheby's, Geneva, in November 2010.

“The market for colored stones is strong because of their rarity,” said Guy Burton, a director at the London-based jeweler Hancocks. “People buy them for investment purposes, and they can be seen as a hedge against what happens in other markets.”

“The Premier Blue,” as it has been named, is the largest round fancy vivid stone of that color to have been graded by the Gemological Institute of America, said Sotheby's, who have not revealed the identity of the seller.

It was sourced from the Premier (formerly known as Cullinan) mine near Pretoria, South Africa, the world's main provider of blue diamonds, said Sotheby's.

“Round stones are the most popular,” said Burton, “and colored diamonds have an obvious appeal to buyers in Hong Kong and mainland China. If I were a betting man, I'd bet that this should make some kind of record. A lot depends on how aesthetically pleasing it is.”

The pigmentation of blue diamonds is caused by the presence of boron atoms. The higher the concentration of that element, the deeper the color.

“Fancy Vivid” is the third most intense gradation. A 5.30-carat cushion-cut blue diamond graded “fancy deep,” the highest intensity of color, sold for $9.6 million at Bonhams in London on April 24.

The price of $1.8 million per carat was an auction record for a blue diamond, said Bonhams, which had 25 telephone bidders registered for the lot. The buyer at Bonhams was Graff.

Sotheby's 40th anniversary auction of jewels and jadeite in Hong Kong in October will comprise about 330 lots and is estimated to raise more than $77.4 million.